Magnetic memories, particularly magnetic random access memories (MRAMs), have drawn increasing interest due to their potential for high read/write speed, excellent endurance, non-volatility and low power consumption during operation. An MRAM can store information utilizing magnetic materials as an information recording medium. One type of MRAM is a spin transfer torque random access memory (STT-MRAM). STT-MRAM utilizes magnetic junctions written at least in part by a current driven through the magnetic junction. A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction. As a result, layer(s) having magnetic moments that are responsive to the spin torque may be switched to a desired state.
For example, FIG. 1 depicts a conventional magnetic tunneling junction (MTJ) 10 as it may be used in a conventional STT-MRAM. The conventional MTJ 10 typically resides on a substrate 12 and is electrically connected to a bottom contact 14 and a top contact 22. The conventional MTJ 10, uses conventional seed layer(s) (not shown), may include capping layers (not shown) and may include a conventional antiferromagnetic (AFM) layer (not shown). The conventional magnetic junction 10 includes a conventional pinned, or reference, layer 16, a conventional tunneling barrier layer 18, and a conventional free layer 20. Conventional contacts 14 and 22 are used in driving the current in a current-perpendicular-to-plane (CPP) direction, or along the z-axis as shown in FIG. 1.
The conventional pinned layer 16 and the conventional free layer 20 are magnetic, while the conventional tunneling barrier layer 18 is nonmagnetic. The magnetization 17 of the conventional pinned layer 16 is fixed, or pinned, in a particular direction. The conventional free layer 20 has a changeable magnetization 21. Although depicted as simple layers, the free layer 20 and conventional pinned layer 16 may also include multiple layers. The pinned layer 16 and free layer 20 may have their magnetizations 17 and 21, respectively oriented perpendicular to the plane of the layers. However, the magnetizations 17 and 21 of the conventional pinned layer 16 and free layer 20 may be in plane.
To switch the magnetization 21 of the conventional free layer 20, a current is driven perpendicular to plane (in the z-direction). When a sufficient current is driven from the top contact 22 to the bottom contact 14, the magnetization 21 of the conventional free layer 20 may switch to be parallel to the magnetization 17 of the conventional pinned layer 16. When a sufficient current is driven from the bottom contact 11 to the top contact 22, the magnetization 21 of the free layer may switch to be antiparallel to that of the pinned layer 16. The differences in magnetic configurations correspond to different magnetoresistances and thus different logical states (e.g. a logical “0” and a logical “1”) of the conventional MTJ 10.
Because of their potential for use in a variety of applications, research in magnetic memories is ongoing. For example, mechanisms for improving the performance of STT-RAM are desired. Accordingly, what is needed is a method and system that may improve the performance of the spin transfer torque based memories.